The present invention is directed to electrical driver apparatuses used for driving electronic devices, such as laser diode devices. The present invention is especially directed to driver apparatuses having low minimum driver signal voltages in high speed bipolar circuits.
In present day driver apparatuses, there is a need for providing AC (alternating current) coupling between a driver apparatus and the device that is driven by the driver apparatus. This is so in order to maintain appropriate voltage at a driver transistor in order to avoid operating the driver transistor in saturation, which would significantly slow the operation of the driver apparatus. A consequence of having to establish AC coupling in order to keep a driver transistor from operating in saturation is that extra components must be included that reduce the overall system performance and increase the overall system cost.
Prior art driver apparatuses are commonly configured to employ driving a differential pair of bipolar transistors to generate the required drive signals. Driving a differential pair of bipolar transistors with high speed switching causes a prominent overshoot in collector current of the respective transistor of the driven transistor pair that is turning on. The overshoot distorts the driver signals from the ideal step current waveform that is desired so that error rates may be minimized.
There is a need for a driver apparatus that avoids the necessity of providing AC coupling with a driven device.
There is a need for a driver apparatus that exhibits a lower minimum drive potential than is attainable by prior art drive apparatuses in order to better accommodate low supply voltage limits.
There is a need for a driver apparatus that avoids driving a differential pair of bipolar transistors with high speed switching in order to avoid overshoot in collector current of the respective transistor of the driven transistor pair that is turning on.